#include <iostream>

using namespace std;



class C1
{
    int m_A; //默认是私有权限
};

struct C2
{
    int m_A; //默认是公共权限
};
int main() {
    C1 c1;
    c1.m_A = 10; //错误，访问权限是私有
    
    C2 c2;
    c2.m_A = 10; //正确，访问权限是公共

    return 0;
}